This invention relates to trunnion bearing assemblies for coupling elements which must undergo relative movement and more particularly to such bearing assemblies which provide a ball and socket action.
Ball and socket joints are extensively used in a variety of devices to provide for pivoting movement of one element relative to another about a principal pivot axis while providing some limited freedom of movement at right angles to the primary motion. In some usages, trunnion bearing assemblies may be subjected to heavy loads, sudden shock forces, and abrasion. Under these circumstances strength and durability are highly important considerations. Trunnions bearing assemblies are used, for example, to couple the push arms of a bulldozer attachment to the sides of a tractor. In this usage the bearings may be subjected to the severe operating conditions described above and expensive and time consuming repairs or replacement are frequently necessary.
The most common form of ball and socket trunnion joint employs a ball formed as an integral element with the supporting trunnion shaft. It is difficult to design such a ball and socket joint for maximum durability in part because of the practical problems involved in heat treating the bulky metal ball to obtain a desired combination of interior strength for resisting breakage coupled with surface hardness for resisting wear. As different forms of heat treatment are required for these two purposes, the result has been an undesirable compromise wherein the interior of the ball element has less strength than would be desirable while the surface is less hard than would be desirable. Consequently, case crushing, chipping, and rapid wear occur at the surface and breakage is common. When failure or serious deterioration has occurred, the entire ball and trunnion element must be replaced.
It has heretofore been proposed to form the trunnion as a two piece element in which the necessary spherical surface is on a replaceable sleeve which fits coaxially on a cylindrical trunnion shaft. This construction has the potential for alleviating the problems discussed above. The spherically surfaced sleeve may more easily be heat treated to a desired hardness while the shaft on which the sleeve is disposed may be separately heat treated for maximum strength. As heretofore designed, replaceable sleeve trunnion bearings of this kind have been undesirably costly and complex and have been difficult to assemble and reassemble. Heretofore the replaceable sleeve has been secured to the supporting trunnion shaft either by welding or by complex bulky retainer means which adds substantially to the cost and size of the assembly and which require a complicated series of operations in order to replace the spherical surface sleeve.